Biology

[Livvy77]

Hi, I am really stuck on this question, I am just wondering if anyone knows how to do it?

In human beings the gene for brown eyes is dominant over the gene for blue eyes. A brown-eyed man marries a blue-eyed woman and they have five children. Three of the children have brown eyes and two have blue eyes.
What are the genotypes of the mother, the father, and the children, explain how you arrive at your answer?

Thank you in advanced!

[Gizmonster]

It's a LONG time since I've done Biology, co I could be completely wrong, but this is my attempt to start you off in the right direction:
The mother either has blue-blue, or blue-X, where X is a less dominant gene than blue (say green for example).
The father cannot have brown-brown; otherwise every child would have brown eyes; so he has brown-Y, where Y is a less dominant gene than brown.
Does this help ya ??
(Feel free to correct me if I'm wrong!!)

[Livvy77]

Thank you! That has really helped!

[slaney]

There are a few similar questions with answers here which should help you...
http://biology.clc.uc.edu/courses/bio1081l/geneprob.htm

[pixie373]

Mother has blue-blue. Father has brown-brown or brown-blue. He still has brown eyes, because the brown is dominant. The brown-eyed children will all have brown-blue and the blue-eyed, blue-blue (one from each parent).

[pixie373]

^^so the father's must be brown-blue.

[Livvy77]

Thank you!

[Gizmonster]

I don't think there's enough information to give you a definite answer.
The father could be brown-blue and the mother blue-blue; or the father could be brown-blue and the mother blue-green; or the father could be brown-green and the mother blue-blue; or the father could be brown-green and the mother blue-green (although this option does lead to the possibility of green eyed children).
I'm guessing that as there is no mention of green eyes, etc, the first option is most likely what the question setter is after - father brown-blue and mother blue-blue.

[Livvy77]

Okay, thank you!

[Peter Pedant]

No Giz at this level
it is obvious Livvy should stick to blue/brown only

I agree that in real life the situation is different

[wildwood]

All things being equal......

Father is Bb - brown but carrying the blue.
Mother is bb - blue
Brown eyed kids have Bb - same as father.
Blue eyed kids have bb - same as mother.

The mother can only pass the (b) blue gene on.
The father can pass either the (B) brown or the (b) blue gene.

This is only correct concerning the brown and blue gene. There are other eye colour mutations which may affect the brown or blue colour to a degree that a blue eye may appear brownish or visa versa.

[Old_Geezer]

I suspect you have two personas here ?